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SR 520 - West Approach Bridge North Project - Completed December 2017

Project news

The SR 520 West Approach Bridge North Project is complete.

Why is WSDOT reconstructing the SR 520 corridor?
The SR 520 Bridge Replacement and HOV Program is enhancing public safety and mobility by replacing the highway's aging, vulnerable bridges and making significant transit and roadway improvements throughout the corridor. The construction program's planned improvements extend from I-5 in Seattle to I-405 in Bellevue.

The End Result
The West Approach Bridge North is the most recently completed piece of the SR 520 Bridge Replacement and HOV Program. Opened to traffic in summer 2017, the new approach bridge extends SR 520’s three westbound lanes and the SR 520 Trail from the floating bridge to the Montlake area in Seattle. We are building a parallel West Approach Bridge South, for eastbound traffic, as part of the upcoming Montlake Phase of SR 520 construction.

Project Benefits

Improves safety

The old 1963-era west approach bridge is a fixed structure supported by hollow columns, and is vulnerable to a catastrophic earthquake. The new West Approach Bridge North, built to current earthquake standards, is designed to withstand a magnitude of earthquake that’s expected to happen only once in 1,000 years.

Eastbound SR 520 traffic currently travels from Montlake to the new floating bridge on the old west approach structure. While we remove the old bridge and construct a replacement, both eastbound and westbound traffic will travel between Montlake and the floating bridge on the West Approach Bridge North, with two lanes in each direction.

Relieves congestion

The new West Approach Bridge North extends SR 520’s three westbound lanes (including an HOV/transit lane) to Montlake. The bridge also includes a wide shoulder that allows vehicles to pull over, without blocking traffic, in case of a breakdown.

Provides multimodal options

The new approach bridge extends the 14-foot-wide SR 520 bicycle and pedestrian trail across Lake Washington, providing a new cross-lake connection.

The addition of transit/HOV lanes and a cross-lake shared-use trail provide greater reliability and more travel options to accommodate growth in the region.

Protects environment

The new approach bridge expands access and facilities for public transportation and nonmotorized transportation options with low carbon emissions.

The project removed from the Washington Park Arboretum the old westbound off-ramp and unused R.H. Thomson “Ramps to Nowhere” – part of WSDOT’s commitment to help restore the Arboretum.

The SR 520 Program has also participated in numerous mitigation projects to protect the natural environment of the greater Lake Washington watershed. Learn more about these projects and other environmental benefits on our SR 520 - Environmental Stewardship page.

What is the project timeline?

September 2014: Began construction

July 2017: Opened new westbound off-ramps to Montlake area

August 2017: Opened new bridge to traffic

December 2017: Opened SR 520 Trail between Montlake and new floating bridge

Financial Information
The project was funded by a variety of state and federal sources. The final cost of the West Approach Bridge North Project was approximately $210 million.

Partnerships and cooperation

WSDOT and its contractors worked closely with local, state and federal officials, Native American tribes, regulatory agencies, environmental groups, community organizations, transit agencies and many others during the planning, design and construction of the new West Approach Bridge North. These partnerships helped inform a number of construction documents, including the Neighborhood Traffic Management Plan (pdf, 1.37 mb) and the Seattle Community Design Process Final Report (pdf, 21.9 mb).

2006 photo of a damaged hollow column on the existing west approach bridge that has since been repaired. The columns for the West Approach Bridge North Project are built to modern earthquake standards.